If it really came down to it, and you did have to defend yourself against an interstellar attacker, would a traditional gun actually be able to do the trick? Let's gaze at the idea, and crunch some numbers to find out.

The idea that just about anyone with access to a 3D printer could spit out a gun with a few clicks was disconcerting, but the person firing the thing was putting themselves in just as much danger as the person on the other end. Until now.